Alloy steel



Patented June 28,` 1949 (Cl. 'i5-423) 7 Claims.

Thisnventin frtes t-'lit steers and more "paitlnlarly tvo Tow alloy;tensile strength steels adapted for ntnf ctmt'ff` trates 'suite maarweidingty t'fnfn al methods.

f'Afrtherfobjt of fthe vent' n'is the provisidn'nfsuth 'an alloy 'stt'"n a `'specific lion'ileinaticir'l5 `ofy alltiu'yiirgl el'een'ts can bevaried Within definite "ranges ttclvlrrvi'tle proper Weldalldilityandstrength y'for i'a'r'yirig thicknesses of bate.

The ffore'goin'g 'objects' are 'achieved I:in the prsentnvention by theprei'zislc'i` Lofi afew A'and useful tomltinationfor` 'allowingleriientsfwmch to'- gether with iron are combined to give an alloy steelhaving the desi/fable tensile properties, toughness Aand `dut'stility"common lto present day rW 'alloy or niild alloy-steels together withiinprovedweldin'g characteristics.

fHigh tensile ialloy'stels intended for welded plate fabrication haveheretofore `beensubject to serious shortcomings. `yWhen a plate of steelis Welded by gas, nt'allior'carbon arc, or electrical resistanceinetlids, a'ae 1vcalled the heat affectdzone, nxt Ito theffused Weld'`metal, is heated t"t/inpe`ratres vra'iigir'ig fron the lowercriticaflpont up to the-melting rangeof the a1- loy. nfterthe weldingoperation, `'as this zone cools, the steeltherein may under certainconditions become excessively hard, even to the extentudf :acquiringcrlckstwhichrare sometimes 'referred to'r'as :underbead J'cracks. The'hardening j tendencyin the w heat affecteazoneis aggravated when thecarbon content:of'thefalloyfis increased ,Qra certain alloying elementsare added to raise the strength of the steel.`

In the p'a'st'; it has beenrnecessary for the steel industry todoptoneormore costly and laboriols expediente` "to avoid excessive hardening andcracking duringweldingmoperations. One `such expedient to .restrictthey. carbont content of `the steel` to 4less than about 0.12per cent,The actual percentage of certain widely used alloy steels;` fabricated-'into tpl'ate'is fabut'fOlOQ to 0.1 l 'per cnt. Whenltlecarbon ntentfisrestricted 'in 'this 'frxiannen "itfi'sn'fnecessary-tb add lrelativelylarge 'and Acostly-zt11"1'c1iit;s of 1"alloying: elements tof providestrengthinf the lultilnate composition."Presentfcomrnercialhighrtensile'isteels intended fior Welding c'contain'relatively large f amounts of "ffmanganese, vchronuin, artiekel;rccpper., and tpnosto prehat them, 'er to.l emiploiexpensive electrodes.

According tbV purfinve'n cwy alleys-steel is prvidledrofnighfterfsil@properties-tand ofr'siitable 'euctnity `Satin-1tinignnesswitnutftr'eehardfenability common to the manganese steels of the pirfrt.Qur steels contain between 0.12 and 0.201-per`fcentl carbon `andbetweenl `0.40 ialtid'OlQO percentmanganese.-

Wherasfin the'rpr-ior artf,-steelswith 290 cent manganeselsslhiftiloenlfsftilsf ry frornthe-pirit of viewofstifng l vflfcyi'ld-pint, We*have discovereda combination o allo ""g "elrnentsvvhich enables-ustolimitthe"` e `content to 0290 per cent or .below-r whil the sametiineobtaining the necessari/physicalSpiperties.

` Our invention obviates `the necessityfofff'addii'g any chromium inobtaining the desired propirties 'and "pf tb'-iep VtloW `aspossibleLaridfinaiyfcase, iit'irilperfent of the steel.

mild imprvern'erit 'in strengthtitvitnouttcitically increasingthethardra'bilitymf mirc-steels. Thus,

inches, we sometimes find it desirable to increase Y the tensilestrength f the ultimate composition by the addition of nickel suicientto raise the total nickel content to between 0.50 and 1.0 per cent. Suchaddition does not critically increase the hardening characteristics ofthe alloy in the *Y heat affected zone of the weld;

the total phosphorus is maintained below a maximum of 0.08 per cent.

Our steels contain between 0.50 and 1.50 per cent silicon and informulation of individual heats *according to our invention we prefer toadjust the amdunt of manganese employed within l the limits above statedin proportion to the amount of silicon. Thus, when 0.50 per cent of 1silicon is employed we use in the neighborhood of 0.40 per cent ofmanganese which is near the lower limit of the operable range ofamounts,

while, on the other hand, when higher percentages of silicon areemployed, the amount of manganese is proportionately increased.

In our steels, improved welding properties are obtained by the additionof titanium in conjunction with another alloying element. The elementused in conjunction with titanium can be molybdenum or vanadium orcolumbium or zirconium. The amount of titanium employed is between 0.03and 0.20 per cent of the steel and the amount of the additional elementused in conjunction therewith is between 0.10 and 0.45 per cent.

Thus, a steel prepared according to our invention will conform to thefollowing analysis:

Chromium 0.20 maximum The remainder is iron containingimpuritiesincidental to the commercial production of steel.

We have found that alloy steels within the foregoing ranges will providea high tensile steel having yield strengths comparable to or `superiorto other high strength steels now used in the industry together withgreatly reduced hardenability characteristics under the influence ofwelding. Thus, careful hardness measurements made with a Knoop orVickers diamond indenter scarcely ever-show a hardness in excess of 300in the heat effected zone after welding. Likewise, steel formulated withthe above alloying ingredients in the range of proportions statedexhibit freedom from underbead cracking even ,under severe weldingconditions. i

of our invention, we have discovered that a combination ofY carbon,manganese, and'silicon within the above ranges together'with acombination of titanium and another allo-ying element selected from thegroup consisting of molybdenum, zirconium, vanadium and columbiumprovides a novel combination of high strength and improvedweldabilityfin steel together with freedom from objectionable alloyingelements. In practicing our invention, titanium is combined with one ofthe elements in the aforesaid group in a ratio of about 1 part titaniumto between 3 and 8 parts of said element. Thus, the steel may contain,for example, 0.10 per cent vanadium and 0.03 per cent titanium, or asanother example 0.05 per cent titanium may be combined with 0.18 percent molybdenum, and a third example is the use of 0.04 per centtitanium with 0.12 per cent zirconium. In using columbium, we prefer toemploy about 0.40 per cent in conjunction with 0.05 per cent titanium.We prefer that the amount of titanium plus the amount of one of theaforesaid four elements with which it is combined should be limited to atotal of between 0.13 and 0.50 per cent of said steel.

It will be seen that alloy steels made in accordance with theseprinciples readily provide considerably higher yield points togetherwith improved weldability than is possible under the present art. Forexample, practically all the present commercially deyeloped highstrength steels are made to-only 45,000 p. s. i. minimum in plates overone-half inch thick. Using our invention we have readily producedseven-eighths inch thick plates-ihaving yield points of 50,000 to 63,000pounds per square inch. A steel prepared in these ranges had thefollowing chemical analysis and physical properties:

A preferred composition for the production of one-half inch plate ofimproved welding characteristics is obtained from a heat correspondingto the following analysis:

Percentage Carbon 0.14 Manganese 0.65 Silicon 0.75 Molybdenum 0.18Titaniume 0.05 Phosphorus 0.06 maximum Sulphur 0.04 maximum For a moredetailed presentation of the advantages of low weld hardenabilitycoupled with high-tensile strength properties, reference is made to ourarticle entitled: Some observations on the welding of manganese steels,Thei Welding Journal Research Supplement, October, 1944.

Steels conforming to the analyses herein de- In order more particularlyto denne the nature ,scribed and claimed .exhibit Jominy curves verysimilar to that shown for heat 421 in Fig. 7 of the reference article.

Having thus described our invention with the aid of illustrativeexamples, it is to be understood that our invention is not to be takenas limited thereto, the scope of the invention being dened by theappended claims wherein the particular ranges of amounts specined maybe, of course, subject to slight variations Without departing from thespirit of the invention.

We claim:

1. A low alloy, high tensile steel suitable for the production of plateshaving improved weldability, said steel containing 0.12 to 0.20 per centcarbon, 0.40 to 0.90 per cent manganese, 0.50 to 1.50 per cent silicon,0.08 per cent maximum phosphorus, 0.04 per cent maximum sulphur, 0.20per cent maximum chromium, from a trace to 1.0 per cent nickel, from atrace to 0.35 per cent copper, 0.03 to 0.20 per cent titanium, 0.10 to0.45 per cent of an element selected from the group consisting ofmolybdenum, zirconium, vanadium and columbium, the remainder beingsubstantially all iron.

2. A low alloy, high tensile steel suitable for the production of plateshaving improved weldability, said steel containing 0.12 to 0.20 per centcarbon, 0.40 to 0.90 per cent manganese, 0.50 to 1.50 per cent silicon,0.08 per cent maximum phosphorus, 0.04 per cent maximum sulphur, 0.20per cent maximum chromium, from a trace to 1.0 per cent nickel, from atrace to 0.35 per cent copper, titanium and an element selected from thegroup consisting `of molybdenum, zirconium, vanadium and columbium, theratio of the amount of titanium present to that of said element beingbetween 1 to 3 and 1 to 8 and the total amount of titanium and saidelement being from 0.13 to 0.50 per cent of said steel, the remainderbeing substantially all iron.

3. A low alloy, high tensile steel suitable for the production of platesup to about one inch thick having improved weldability, said steelcontaining 0.12 to 0.20 per cent carbon, 0.40 to 0.90 per centmanganese, 0.50 to 1.50 per cent silicon, 0.08 per cent maximumphosphorus, 0.04 per cent maximum sulphur, 0.20 per cent maximumchromium, 0.25 per cent maximum nickel, from a trace to 0.35 per centcopper, 0.03 to 0.20 per per cent titanium and 0.10 to 0.45 per cent ofan element selected from the group consisting of molybdenum, zirconium,vanadium and columbium, the remainder being substantially all iron.

4. A low alloy, high tensile steel suitable for the production of platesfrom about 3A inch thick to about 21/2 inches thick having improvedWeldability, said steel containing 0.12 to 0.20 per cent carbon, 0.40 to0.90 per cent manganese, 0.50 to 1.50 per cent silicon, 0.08 per centmaximum phosphorus, 0.04 per cent maximum sulphur, 0.20 per cent maximumchromium, 0.50 to 1.0 per cent nickel, from a trace to 0.35 per centcopper, 0.03 to 0.20 per cent titanium and 0.10 to 0.45 per cent of anelement selected from the group consisting of molybdenum, zirconium,vanadium and columbium, the remainder being substantially all iron.

5. A low alloy, high tensile steel suitable for production of plateshaving improved Weldability, said steel containing 0.12 to 0.20 per centcarbon, 0.40 to 0.90 per cent manganese, 0.50 to 1.50 per cent silicon,0.12 to 0.25 per cent molybdenum, 0.03 to 0.20 titanium, 0.08 per centmaximum phosphorus, 0.04 per cent maximum sulphur, 0.20 per cent maximumchromium, from a trace to 1.00 per cent nickel and from a trace to 0.35per cent copper, the remainder being substantially all iron.

6. A low alloy, high tensile steel suitable for the production of plateshaving improved weldability, said steel containing 0.12 to 0.20 per centcarbon, 0.40 to 0.90 per cent manganese, 0.50 to 1.50 per cent silicon,0.10 to 0.20 per cent zirconium, 0.03 to 0.20 per cent titanium, 0.08per cent maximum phosphorus, 0.04 per cent maximum sulphur, 0.20 percent maximum chromium, from a trace to 1.00 per cent nickel and from atrace to 0.35 per cent copper, the remainder being substantially alliron.

7. A loW alloy, high tensile steel suitable for the production of plateshaving improved Weldability, said steel containing 0.12 to 0.20 per Centcarbon, 0.40 to 0.90 per cent manganese, 0.50 to 1.50 per cent silicon,0.20 to 0.45 per cent columbium, 0.03 to 0.20 per cent titanium, 0.08per cent maximum phosphorus, 0.04 per cent maximum sulphur, 0.20 percent maximum chromium, from a trace to 1.00 per cent nickel and from atrace to 0.35 per cent copper, the remainder being substantially alliron.

ALVIN G. WAGGONER. WILLIAM B. BROOKS.

REFERENCES CITED The following referenlces are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 1,261,743 Churchward Apr. 2, 19181,839,157 Mathesius Dec. 29, 1931 2,040,189 Strauss May 12, 1936 FOREIGNPATENTS Number Country Date 118,263 Switzerland Dec. 16, 1925 OTHERREFERENCES Alloying Elements in Steel, pages and 66; edited by Bain,published in 1939 by the American Society for Metals, Cleveland, Ohio.

Making, Shaping and Treating of Steel, 5th edition; edited by Camp andFrancis, published in 1940 by The Carnegie-Illinois Steel Corporation,Pittsburgh, Pa.

Metals and Alloys, February 1939, pages 48 and 49.

